1. Field of the Invention
The present invention generally relates to an optic switch, and more particular to an optic switch employing multiple reflections of optic signals to realizing switching of optic outputs.
2. The Related Arts
Optic switches are widely used in optic networks. The optic switches are usually classified as mechanical type and non-mechanical type. The mechanical type optic switch realizes switching operation between two or more outputs by moving optic fibers or optic elements with mechanical or electromagnetic means. Since an optic fiber is generally very thin, moving the optic fiber to switch between outputs is risky and may cause undesired loss of optic signals. On the other hand, moving an optic element, rather than a fiber, to perform switching operation is more advantageous. Such a method has only a cost of an insertion loss of less than 2 dB but gains a high isolation, sometimes as high as 45 dB. In addition, it is independent of polarization and wavelength of the incoming optic signals. The commonly used optic elements in such a switching device comprise reflectors, lenses, and prisms but not limited thereto, among which reflectors are the most common optic element that is moved to realize switching operation.
U.S. Pat. No. 5,042,889 teaches an optic switch that realizes switching operation by moving a reflector. FIGS. 1 and 2 of the attached drawings illustrate an operation principle of the optic switch. Two optic inputs 130, 150 and two optic outputs 140, 160 are respectively aligned with each other forming two intersecting optic paths between the input and output 130, 140 and the input and output 150, 160 as shown in FIG. 1. By placing a reflector 170 having opposite reflective surfaces 171, 172 (FIG. 3 of the attached drawings) at the intersection of the optic paths, the input signal from the optic input 130 is reflected and redirected by the reflective surface 171 toward the optic output 160, while the input signals from the optic input 150 is reflected and redirected by the reflective surface 172 toward the optic output 140.
Since theoretically, the intersection of the optic paths is a single point, while the reflector that possesses two opposite reflective surfaces is always of a thickness, no matter how small it may be, between the reflective surfaces. As a consequence, only one of the reflective surfaces can be truly located at the intersection point to reflect and precisely redirect the input signals to the new output, while the other one is not. This is shown in the enlarged view of FIG. 3 wherein the reflective surface 171 is exactly located at the intersection point so that the input signals from the input device 130 can be precisely redirected to the output device 160. However, the reflective surface 172 cannot be exactly located at the intersection point and the input signal from the optic input 150 is redirected to the optic output 140 along an offset and non-aligned path indicated by the dashed line shown in FIG. 3. This causes a large signal loss.
It is desired to have an optic switch for overcoming the above problem.
Accordingly, an object of the present invention is to provide an optic switch, especially a 2xc3x972 optic switch, that is capable to selectively and precisely redirect input signals from two optic inputs toward two optic outputs to realize optic switching operation without significant signal loss.
Another object of the present invention is to provide a mirror type optic switch comprising an additional reflective surface for precisely redirecting input signals to an optical output by means of multiple reflections.
To achieve the above objects, in accordance with the present invention, an optic switch includes a casing to which first and second input devices and first and second output devices are attached. The first input and output devices are aligned with each other and the second input and output devices are aligned with each other. A movable reflection device is movable between a non-engaged position and an engaged position between the input and output devices by a driving device. The movable reflection device has first and second reflective surfaces. A fixed reflection device is fixed inside the casing and has a third reflective surface which is parallel to and opposes the first reflective surface when the movable reflection device is at the engaged position. When the movable reflection device is at the non-engaged position, optic signals from the first and second input devices are allowed to directly pass to the first and second output devices respectively. When the movable reflection device is at the engaged position, the optic signal from the second input device is reflected and redirected by the second reflective surface to the first output device and the optic signal from the first input device is reflected at least three times by the first and third reflective surfaces and redirected to the second output device. Thus a switching operation is realized.
The instant application is essentially of a detailed embodiment of the copending application titled xe2x80x9cOPTICAL SWITCH WITH MOVABLE MIRRORxe2x80x9d filed Dec. 24, 2001 with an unknown serial number while having the same applicants and the same assignee as the invention. The basic principle of the instant invention is disclosed in such a copending application and should be referred thereto.